What does the cryptic crossword clue "Star out last is dispersed in thick cloud (11)" mean?

The definition is "cloud". The wordplay uses an anagram. anagram of STAR + OUT + LAST = ALTOSTRATUS; definition: "cloud" The answer is ALTOSTRATUS.

Star out last is dispersed in thick cloud (11)

Times Cryptic #28104 | 28 Across | 2021-10-09 flower